the encryption of yoru wallet.
but the best thing to do is leave ur wallet unencrypted because I heard stories on this forum about ppl not knowing their passwords.
I think if u just keep ur wallet.dat under close lock, u kno not sharing it with anyone, keeping it offline, then no one in the world will be able to access it.
delete ur wallet.dat from ur pc and keep it on like 2 - 3 USB drives.
if u need to use LTC, then use a clean computer to upload ur wallet.dat and go from there.